The distribution of blood flow to different areas of skin on the back of rabbits was determined by 131I-labelled macroaggregates of albumins, given intracardially in a single dose. The radioactivity was determined in 3 concentric standard samples of skin punched out of each skin area. Inflammation was induced in the areas on the right side of the back by intracutaneous injection of turpentine, the corresponding areas on the left side serving as controls. Turpentine injections were given at different intervals, up to 16 h, before determination of blood flow distribution. In normal skin, the blood flow was similar in corresponding areas on the right and left side of the back. However, it differed significantly from one area to another along the back. Turpentine inflammation was found to be associated with a diphasic increase of blood flow; an early phase completed in 2–3 h, followed by a late, more prolonged, phase. In the early phase, blood flow was markedly increased in the central zone (about 1 cm2), much less so in the intermediate and peripheral zones of the areas studied. In the late phase, blood flow was uniformly increased in the whole area (about 10 cm2). The vascular reaction to turpentine was found to be significantly influenced by the location of the inflamed area. Turpentine caused the highest blood flow in the areas which had the highest flow under normal condition